(n.) The quality or state of being rational; agreement with reason; possession of reason; due exercise of reason; reasonableness.

IQ Vernunft admissibility apprehension balance brain brains caliber capacity common sense comprehension conception contact with reality cool head coolheadedness coolness deduction deductive power deductive reasoning demonstration discourse discourse of reason discursive reason down-to-earthness due sense of earthiness esemplastic power esprit freedom from illusion good sense gray matter hardheadedness head headpiece healthy mind horse sense ideation induction inductive reasoning integrative power intellect intellection intellectual faculty intellectual grasp intellectual power intellectualism intellectuality intelligence intelligence quotient justifiability justness knowledge lack of feelings level head levelheadedness logic logical thought logicality logicalness lucid interval lucidity matter-of-factness mens mental age mental balance mental capacity mental equilibrium mental grasp mental health mental hygiene mental poise mental ratio mentality mind mother wit native wit normalcy normality normalness nous philosophy plain sense plausibility positivism power of mind power of reason practical mind practical wisdom practical-mindedness practicality practicalness pragmaticism pragmatism proof psyche ratio ratiocination rationalism rationalization rationalizing realism reason reasonability reasonableness reasoning reasoning faculty reasoning power right mind sanemindedness saneness sanity scientism scope of mind secularism sense senses sensibleness smarts sober senses sober-mindedness soberness sobriety sophistry sound mind sound sense soundness soundness of mind specious reasoning sweet reason thinking power understanding unidealism unromanticalness unsentimentality wholesomeness wit worldliness